Method of making a fat coated meat product

ABSTRACT

A meat based product is extruded as an elongate billet 14 from the head 10 of a mandrel 1. The mandrel 1 has inner and outer passages to coextrude a meat core and a fat annular coating from the head into an outer casing 13.

This invention relates to the manufacture of a food product of constantcross section with a relatively solid main body or core and a thinnerouter layer of less solid, relatively mobile material. One exemplaryproduct with which the invention is specially concerned comprises a coreof turkey or other meat and a relatively thin uniform outer layer of fatwithin which the meat is cooked.

The mass-production of a food product of the kind set forth abovepresents a problem owing to the physical dissimilarity between the coreand outer layer. The technique of rendering the core and outer layerphysically homogeneous by, for example heating is not appropriate to thefood industry.

According to the present invention a method of manufacturing a foodproduct with a relatively solid core and a more mobile outer layercomprises coextruding the core and outer layer into a casing dispensedfrom the extrusion head. The casing has a closed end immediately infront of the head before extrusion commences and as the extruded foodproduct advances from the head the casing is carried with it. The casingis a sufficiently close fit on the outer layer to preserve the coherentand even extruded form to provide a product such as would be obtained bythe concentric co-extrusion of two physically similar extrudablesubstances.

When the desired length of product has been extruded the product is cutand the casing closed around the rear end; the means effecting theclosure preferably also closes the front end of the casing of theproduct behind at a position immediately in front of the extrusion head.

Thus the essence of the invention is the dispensing of the casing fromthe extrusion head to contain the mobile outer layer and this canconveniently be contrived by extruding from an elongate mandrel with thecasing stock stored around the outer periphery of the mandrel.

The invention will now be described by way of example and with referenceto the accompanying drawings wherein:

FIG. 1 is a partially schematic elevation view of an apparatus forputting the present invention into effect;

FIG. 2 is a side view partly in section of the extrusion mandrel of theapparatus of FIG. 1;

FIGS. 3, 4 and 5 are sections on the lines III--III, IV--IV and V--V ofFIG. 2;

FIG. 6 is an elevation of the extrusion head of the mandrel;

FIG. 7 is view of the extrusion head with a casing prior to closure andemerging extruded food product;

FIG. 8 is a view similar to FIG. 7 showing the meat product havingadvanced a short distance with the casing closed;

FIG. 9 is a section of the food product on the line IX--IX of FIG. 8;and

FIGS. 10, 11 and 12 are schematic plan views illustrating how a foodproduct in the form of an elongate billet leaves the mandrel and isdischarged into a freezing tank.

Referring initially to FIG. 1 of the drawings the apparatus illustratedcomprises an extrusion mandrel 1 fed with large intact natural pieces ofturkey or other meat A from a first hopper 2 by a vane pump in housing 3and with liquified fat material B from a second hopper 4 by a vane pumpin housing 5. The meat is raw and deboned and preferably mechanicallymassaged with salt to produce salt-soluble proteins which enhance thebonding properties of the meat. Pipes 6 and 7 extend from the hoppers 2and 3 respectively to central passage and the surrounding annulus ofmandrel 1 as will be described with reference to FIGS. 2 to 5. Pipe 6 issupported by stand 8. A cutting, closing and clipping apparatus 9 ispositioned over the extrusion head 10 of mandrel 1 and has a reel 11dispensing clipping stock 12. Thin, approximately 20 microns, tubularcasing stock 13 of non-toxic transparent plastics is threaded onto themandrel 1.

A tiltable track 15 supported on legs 16 receives the elongate casedbillet 14 extruded from mandrel 1. When finally discharged, billet 14 istipped sideways through flaps 17 into a freezing tank 18. This tippingand the necessary starting and stopping of the extrusion process, aswill be described subsequently with reference to FIGS. 10 to 12, iseffected by microswitches 19 and 20.

The detailed construction of the extrusion mandrel 1 will now bedescribed with reference to FIGS. 2 to 5 of the drawings.

The elongate extrusion mandrel 1 has inner and outer concentric sections20 and 21 of circular cross section. The inner section 20 provides thetotally unobstructed passage necessary for the passage of turkey meat Awhich is solid in consistency often comprising large intact naturalpieces. An axial inlet 25 at the rear end of the inner section 2 allowsthe entry of this meat from pipe 6 (see FIG. 1). The mandrel outersection or casing 21 defines with the inner section 20 a separateannular space 22 through which the mobile fluid fat B forming the outerlayer of the food product flows. A radially extending pipe 23 at therear end of the mandrel 1 provides an inlet for the fat from pipe 7 (seeFIG. 1). As can well be seen from the sectional views, vanes 24 connectthe inner and outer sections 20 and 21.

The extrusion head 10 is formed by the laterally (i.e.,cross-sectionally) enlarged front end part of the mandrel and is seen insection in FIG. 2. The space 22 is constricted here to define an annularfrontwardly facing extrusion orifice 26 which reduces the thickness ofthe extruded fatty layer. The main length of the space 22 through whichthe fat flows is relatively wide to allow free flow of the fat which,though fluid, may be quite viscous especially in the cool ambientconditions usual in the food industry. The frontwardly facing extrusionorifice 27 of passage 20 will, by virtue of increased of cross-sectionalarea, allow the meat some degree of physical relaxation before it entersits casing.

The operation of the apparatus will now be described with reference toFIGS. 6 to 12 of the drawings.

The extrusion head 10 of the mandrel 1 is shown empty in FIG. 6. Onactivation of the extrusion pumps the extrusion product comprising thecore of meat A and annular outer layer of fat B advances to the outletend of the mandrel 1 into the extrusion head 10. This can be seen inFIG. 7. The tubular casing 13 is pulled forward a short distance by handfrom the outlet end of the mandrel, and the apparatus 9 is operated todraw the casing 13 around the front of the emerging billet 14 and tosecure the casing with a front clip 28. The core and annulus of fattymaterial first contact each other as they are coextruded from themandrel into the casing. This position is illustrated in FIG. 8 and itwill be noted that with the advance under extrusion pressure of the meatand fat the billet end part 29 becomes rounded. It should be noted thatthe dimensions of the extrusion head, i.e. the diameters of centralorifice 27 and the width of annular passage 26 are those of the billet14 and the ultimate food product, this being a true extrusion. Thecasing 13 preserves this extruded configuration. FIG. 9 shows the crosssection of the billet and the food product.

Referring now to FIG. 10 the extruded billet 14 with the closed androunded front end part 29 leaves the extrusion head 10 and apparatus 9and travels along the track 15 in the direction x towards themicroswitches 19 and 20. When the front end part of the billet 14contacts and closes the first microswitch 19 extrusion ceases and theapparatus 9 operates to form, close and clip the rear end of the billet14 and the front end of the billet immediately behind. The billet thenresumes its advance driven by means on track 15 to close the secondmicroswitch 20 which operates to tilt the track sideways in thedirection of arrows y thereby tipping the billet through flap 17 intofreezing tank 18. The billets move transversely of their length throughtank 18 and are retrieved frozen for cutting to the desired length andany packaging required.

It should be appreciated that the billet 15 as discharged from theextruder is, in principle, a food product in itself suitable for slicingand cooking. The casing 14 remains on the product right through storage,sale and cooking to the plate. The freezing operation envisaged abovecould thus be supplemented or replaced by a cooking, smoking or otherpreparation.

It should be re-emphasised that although the invention has beendescribed by way of example with reference to turkey meat it isapplicable to any kind of solid raw meat.

The transparent non-toxic casing stock may be of any suitable "skin"material typically of cellulose, polyamide or polyester. One suitablepolyester casing material is sold under the Trade Mark Nalophan.

We claim:
 1. A method of making a meat product with a relatively thinuniform outer layer of fat completely surrounding and directlycontacting the meat and within which the meat is cooked, which comprisespumping relatively solid intact natural meat pieces through a centralpassage of an extrusion mandrel and pumping relatively fluid fattymaterial through a separate annular passage in said extrusion mandrel,increasing the cross-sectional area of the meat to relax the meat andreducing the thickness of the fatty material in a laterally enlargedextrusion head located at the outlet end of the extrusion mandrel,coextruding, through respective orifices in the outlet end of saidextrusion head, the meat, as a core, and the fatty material, as auniform outer annular layer completely surrounding and directlycontacting the meat, directly into a flexible fitting fcasing to formelongated encased billets of the meat product.
 2. A method as claimed inclaim 1 wherein the elongated billets are is subsequently frozen and cutto lengths.
 3. A method according to claim 1 wherein the flexiblefitting casing into which the meat and fatty material are directlycoextruded is taken from casing stock stored on a body portion of theextrusion mandrel behind said extrusion head.